Rheumatoid factor
This examination consists of the tests:
- Rheumatoid Factor Quantitative (RF) (Serum)
- Rheumatoid Factor IgM (RFM) (Serum)
If rheumatoid arthritis is suspected, the test anti CCP is a better parameter to request. The rheumatoid factor measures whether rheumatoid factors are present in the blood and if so, how many.
Rheumatoid Factors (RF) are autoantibodies, or antibodies directed against the body's own structures. They usually belong to the IgM (immunoglobulin M) type, although other types such as IgG and IgA can also occur. These autoantibodies specifically target the Fc portion of immunoglobulin G (IgG).
Autoantibodies mistakenly recognize bodily structures as foreign to the body. Binding to these structures can create immune complexes that cause inflammatory reactions. These inflammations can eventually lead to tissue damage, such as in the joints in rheumatoid arthritis.
Rheumatoid factors do not damage the joints directly but lead to inflammation. These inflammations damage the joint tissue. Rheumatoid factors occur in rheumatoid arthritis, but also in other autoimmune diseases, such as Sjögren's syndrome (chronic inflammation of tear and salivary glands). In addition, they can also occur in long-term bacterial or viral infections. Small amounts of rheumatoid factor can also be found in the blood in healthy people. Thus, rheumatoid arthritis factors are not specific to rheumatoid arthritis.
What does the result mean
Normal
The absence of rheumatoid factor does not necessarily mean that a patient does not have rheumatoid arthritis or Sjögren's syndrome. In about 20% of patients with rheumatoid arthritis, and even more in patients with Sjögren's syndrome, the test for rheumatoid factor is negative (or below the reference value used).
Increased
In complaints suggestive of rheumatoid arthritis or Sjögren's syndrome, elevated levels of rheumatoid factor indicate that the patient probably has rheumatoid arthritis or Sjögren's syndrome. High rheumatoid factor levels in a patient do not always correlate with the severity of symptoms. However, high rheumatoid factor values are often seen in patients with active rheumatoid arthritis.
The test result along with the patient's symptoms determine the diagnosis. In older individuals, a positive test is more often found without the presence of an autoimmune disease, such as rheumatoid arthritis or Sjögren's syndrome. In addition, rheumatoid factor is sometimes found in healthy individuals. Also in patients with endocarditis, tuberculosis, syphilis, cancer, viral infections or diseases of the lungs, liver or kidneys the test for rheumatoid factor is sometimes positive.
Sometimes the symptoms are not very clear yet, and an anti-CCP test can provide additional information so that targeted treatment can be started at an early stage. The combination of the anti-CCP test and the rheumatoid factor (RF) is important for making the diagnosis.
